The invention relates to a device for removing a cement tube remaining in a bone cavity after removing a cemented-in endoprosthesis.
Implants which are embedded in cement cannot generally remain in the bone for an unlimited length of time. If such an implant must be exchanged or removed, an essentially cylindrical bone cement tube remains in the bone after its removal, which must be totally removed for reimplantation.
The removal of the old bone cement was previously carried out by boring it out from above or by laying a bypass at an angle from underneath in order to loosen all bone cement parts using pliers or other mechanical means, in particular suction devices.
It is also known that an extractor, whose head comprises a threaded plug, be used for this purpose by being cut into the bone cement tube in order to obtain a sufficiently firm hold for the removal of the bone cement tube. This known instrument has the weighty disadvantage, that is particular with older patients, it is possible that the bone wall splits open if the radial tension, which is generated by the threaded plug, is greater than the tensile strength of the bone. There is also no guarantee, when using the extractor, that all of the bone cement at the foot end of the bone cavity will be loosened.
A combination of such an extractor with an expanding device is known from German Offenlegungsschrift (published patent application) 29 44 719, whereby the expanding device is used to grip underneath the bone cement tube, in order to ease the removal of the bone cement tube. The use of this device also leads to a substantial mechanical loading of the corticalis which surrounds the bone cement tube. The above described uncertainties, with respect to whether all of the bone cement has been removed, cannot be eliminated by the expanding device. Furthermore, it can be become necessary to enlarge the existing bone cavity in order to grip underneath the bone cement tube to obtain working space for the expanding device underneath the bone cement tube. It is also disadvantageous that an optical supervision of this manipulation and the implementation of the expanding device, for example via an x-ray picture which is transmitted to a monitor, is necessary.